An integrated circuit (IC) is an electronic circuit formed using a semiconductor material, such as Silicon, as a substrate and by adding impurities to form solid-state semiconductor electronic devices (device, devices), such as transistors, diodes, capacitors, and resistors. Any reference to a “device” herein refers to a solid-state semiconductor electronic device unless expressly distinguished where used.
The software tools used for designing ICs produce, manipulate, or otherwise work with the circuit layout and circuit components on very small scales. Some of the components that such a tool may manipulate may only measure tens of nanometer across when formed in Silicon. The designs produced and manipulated using these software tools are complex, often including hundreds of thousands of such components interconnected to form an intended electronic circuitry.
A layout includes shapes that the designer selects and positions to achieve a design objective. The objective is to have the shape—the target shape—appear on the wafer as designed. However, the shapes may not appear exactly as designed when manufactured on the wafer through photolithography. For example, a rectangular shape with sharp corners may appear as a rectangular shape with rounded corners on the wafer.
Once a design layout, also referred to simply as a layout, has been finalized for an IC, the design is converted into a set of masks or reticles. A set of masks or reticles is one or more masks or reticles. During manufacture, a semiconductor wafer is exposed to light or radiation through a mask to form microscopic components of the IC. This process is known as photolithography.
A manufacturing mask is a mask usable for successfully manufacturing or printing the contents of the mask onto wafer. During the photolithographic printing process, radiation is focused through the mask and at certain desired intensity of the radiation. This intensity of the radiation is commonly referred to as “dose”. The focus and the dosing of the radiation has to be precisely controlled to achieve the desired shape and electrical characteristics on the wafer.
A device generally uses several layers of different materials to implement the device properties and function. A layer of material can be conductive, semi-conductive, insulating, resistive, capacitive, or have any number of other properties. Different layers of materials have to be formed using different methods, given the nature of the material, the shape, size or placement of the material, other materials adjacent to the material, and many other considerations.
The software tools used for designing ICs produce, manipulate, or otherwise work with the circuit layout and circuit components on very small scales. Some of the components that such a tool may manipulate may only measure a few nanometers across when formed in Silicon. The designs produced and manipulated using these software tools are complex, often including hundreds of thousands of such components interconnected to form an intended electronic circuitry.
A Field Effect Transistor (FET) is a semiconductor device that controls the electrical conductivity between a source of electric current (source, “S”) and a destination of the electrical current (drain, “D”). The FET uses a semiconductor structure called a “gate” to create an electric field, which controls the shape and consequently the electrical conductivity of a channel between the source and the drain. The channel is a charge carrier pathway constructed using a semiconductor material.
Many semiconductor devices are planar, i.e., where the semiconductor structures are fabricated on one plane. A non-planar device is a three-dimensional (3D) device where some of the structures are formed above or below a given plane of fabrication. A fin-Field Effect Transistor (finFET) is a non-planar device in which a source and a drain are connected using a fin-shaped conducting channel (fin).
In a FET, a gate controls the current flow between a source and a drain—i.e., between two S/Ds—through the fin. The direction of a channel running from one S/D to the other S/D is referred to herein as a channel direction. For the clarity of the description and without implying any limitation thereto, and using the X, Y, Z axes of the coordinate system, the substrate is imagined to be running in an X-Z horizontal plane with the depth of the substrate being in the Y direction, and the fin runs in a vertical Y-Z plane with the width of the fin being in the X direction.
A GAA device includes one or more channels through such that the gate surrounds channel completely in all directions except leaving open the ends of the channel for connections to the source and drain. As an example, if imagined as a pipe, the open ends of the pipe connect to the source and the drain and the gate covers the external surface of the pipe. The gate may cover the surface along the entire length of the pipe (channel) or only a portion of the length of the pipe (channel).
When a GAA device includes multiple channels, each channel can be imagined as a pipe where the set of pipes all run in the same direction from the same source to the same drain. In a GAA device with multiple channels—as used in a non-limiting way to depict and describe various embodiments herein—each channel (pipe) is separately and completely surrounded by the gate material along all or a part of the channel's length between the source and the drain.